Public Time Servers use the Network Time Protocol (NTP) is a protocol for synchronizing the clocks of computer systems and networking equipment over packet-switched, variable-latency data networks. It is designed particularly to resist the effects of variable latency to keep all equipment in sync.
Below is a list of public time servers available for use.
ntp2.usno.navy.mil (220.127.116.11) USNO, Washington, DC
tock.usno.navy.mil (18.104.22.168) USNO, Washington, DC
tick.usno.navy.mil (22.214.171.124) USNO, Washington, DC
time-a.nist.gov (126.96.36.199) NIST, Gaithersburg, Maryland
time-b.nist.gov (188.8.131.52) NIST, Gaithersburg, Maryland
time.nist.gov (184.108.40.206) NCAR, Boulder, Colorado
ntp-s1.cise.ufl.edu (220.127.116.11) University of Florida, Gainesville, FL